Method and apparatus for single particle deposition

Abstract

A method and droplet dispenser for depositing single particles onto a target. For example, a single particle depositing method with improved rate of dispensing single particles and/or increased recovery of rare particles and/or with an extended applicability with different types of particles and/or operation conditions. The depositing method may be capable of increasing the rate of dispensing single cells without decreasing the recovery rate. Testing a single particle condition is combined with testing a zero particle condition and/or the particle type condition. The ejection and sedimentation regions are tested with regard to the presence of a single particle in the ejection, and further particle arrangements allowing a single particle deposition are identified and tested and/or the particle type detection is added to the dispenser control. Accordingly, the speed and recovery rate of dispensing single particles of interest can be improved.

The invention claimed is: 
     
       1. A method of depositing single particles via a droplet dispenser onto a target, wherein the droplet dispenser has a suspension reservoir and a nozzle having an ejection region and a sedimentation region upstream the ejection region, the droplet dispenser being capable of dispensing operation wherein a particle suspension having the particles flows from the suspension reservoir through the nozzle towards a terminal opening of the nozzle at the ejection region and droplets of the particle suspension are dispensed through the terminal opening to the target, nozzle camera is arranged for a particle detection including detecting particles in the particle suspension within the nozzle, a controller is arranged in electronic communication with the nozzle camera and with a testing unit including an image data storage for storing image data of the ejection region and the sedimentation region; the method comprising:
 loading the particle suspension having the particles to the droplet dispenser having the suspension reservoir and the nozzle, wherein the droplet dispenser is capable of dispensing droplets having the particle suspension at a first droplet volume; 
 detecting a presence of the particles in the particle suspension in the nozzle via the nozzle camera; 
 controlling the droplet via the controller dispenser based on a test procedure, which includes
 (i) testing a single particle condition of the droplet dispenser via the testing unit to determine the single particle condition is fulfilled when an ejection region of the nozzle adjacent the terminal opening includes one single particle of the particles and the sedimentation region adjacent to and upstream the ejection region is free of the particles, wherein in the sedimentation region the particles are displaced to the ejection region by sedimentation between the step of detecting the presence of the particles and the step of controlling the droplet dispenser, and 
 (ii) testing at least one of a zero particle condition of the droplet dispenser via the testing unit to determine the zero particle condition is fulfilled when a volume equal to or larger than a 2-fold volume of the ejection region beginning at a tip of the nozzle to the sedimentation region is free of particles to be dispensed, and a particle type condition via the testing unit to determine the particle type condition is fulfilled when the detected particles have a predetermined particle type identified by at least one of size, shape, colour emission and absorption; and 
 
 operating the droplet dispenser via the controller, wherein, in accordance with the testing determinations of
 (i) the single particle condition, and 
 (ii) at least one of the zero particle condition and the particle type condition, one of the droplets is dispensed from the droplet dispenser onto the target or at least one of the droplets is discarded from the droplet dispenser into a collection reservoir. 
 
 
     
     
       2. The method according to  claim 1 , wherein the step of testing the zero particle condition is conducted when the single particle condition is not fulfilled, and includes
 determining the zero particle condition is fulfiled when the volume of the droplet dispenser is free of the particles, wherein 
 the step of operating the droplet dispenser includes discarding at least two droplets from the droplet dispenser when the zero particle condition is fulfilled, and discarding one droplet from the droplet dispenser when the zero particle condition is not fulfilled. 
 
     
     
       3. The method according to  claim 2 , wherein
 when one of the particles is detected within the volume of the droplet dispenser, the step of operating the droplet dispenser includes discarding a number of the droplets from the droplet dispenser required for moving the detected particle from the position within the ejection region. 
 
     
     
       4. The method according to  claim 3 , wherein
 the controller determines the number of droplets to be discarded during the controlling the droplet dispenser step by tracking particles in the nozzle during dispensing droplets, determining a particle displacement per dispensing step and determining the number of droplets to be discarded by dividing the volume that is free of particles by the particle displacement per dispensing step. 
 
     
     
       5. The method according to  claim 3 , wherein
 a number of droplets to be discarded is determined via the controller by partitioning the nozzle into droplet regions being numbered according to the number of droplets required for moving one of the detected particles from the respective droplet region to the ejection region, and determining the number of the droplet region of the one detected particle. 
 
     
     
       6. The method according to  claim 2 , wherein
 the predetermined volume has an axial length along the nozzle equal to a field of view of the nozzle camera used for testing the zero particle condition. 
 
     
     
       7. The method according to  claim 1 , wherein, when the single particle condition within the ejection region is not fulfilled, testing the single particle condition further includes
 reducing the ejection region in size to an ejection region subsection and determining whether the ejection region subsection includes one single particle and the sedimentation region adjacent to the ejection region subsection is free of particles, wherein 
 the step of controlling the droplet dispenser includes dispensing a fractional droplet having a fraction of the first droplet volume onto the target when the single particle condition is fulfilled with the ejection region subsection. 
 
     
     
       8. The method according to  claim 7 , wherein, when the single particle condition within the ejection region subsection is not fulfilled, testing the single particle condition further includes
 reducing the ejection region subsection in size and testing the single particle condition with the reduced ejection region subsection. 
 
     
     
       9. The method according to  claim 7 , wherein
 the step of testing a single particle condition of the droplet dispenser ejection subjection includes testing a plurality of ejection region subsections, each having a different size. 
 
     
     
       10. The method according to  claim 7 , wherein
 the fraction of the first droplet volume is determined by the controller according to the position of the single particle in the ejection region subsection. 
 
     
     
       11. The method according to  claim 1 , wherein the step of testing the particle type condition via the testing unit includes
 defining types of particles in the droplet dispenser by at least one of size, shape, colour emission and absorption, and 
 testing whether the particle in the ejection region is the predetermined particle type, wherein 
 the step of controlling the droplet dispenser via the controller includes dispensing a droplet including the particle having the predetermined particle type onto the target or discarding the droplet into the collection reservoir. 
 
     
     
       12. The method according to  claim 11 , wherein
 the particles include at least two particle types of interest, 
 the step of testing the particle type condition includes determining the particle type of a particle in the ejection region or ejection region subsection, and 
 the step of operating the droplet dispenser includes dispensing a droplet at a target position selected based on the predetermined particle type particle in the ejection region or an ejection region subsection. 
 
     
     
       13. The method according to  claim 12 , wherein
 the step of operating the droplet dispenser includes dispensing droplets from the nozzle on different targets based on different particle types. 
 
     
     
       14. The method according to  claim 11 , wherein
 the particles include one particle type of interest, 
 the step of testing the particle type condition includes determining the particle type of a particle in the ejection region or an ejection region subsection, and 
 if the determined particle type of the particle in the ejection region or the ejection region subsection is the particle type of interest or not, the step of controlling the droplet dispenser correspondingly includes dispensing a droplet at a target position or discarding a droplet. 
 
     
     
       15. A method of depositing single particles via a droplet dispenser onto a target, wherein the droplet dispenser has a suspension reservoir and a nozzle having an ejection region and a sedimentation region upstream the ejection region, the droplet dispenser being capable of a dispensing operation wherein a particle suspension having the particles flows from the suspension reservoir through the nozzle towards a terminal opening of the nozzle at the ejection region and droplets of the particle suspension are dispensed through the terminal opening to the target, a nozzle camera is arranged for a particle detection including detecting particles in the particle suspension within the nozzle, a controller is arranged in electronic communication with the nozzle camera and with a testing unit including an image data storage for storing image data of an ejection region and a sedimentation region the method comprising:
 loading the particle suspension having the particles to the droplet dispenser having the suspension reservoir and the nozzle, wherein the droplet dispenser is capable of dispensing droplets having the particle suspension at a first droplet volume; 
 detecting a presence of the particles in the particle suspension the nozzle via a nozzle camera; 
 controlling the droplet dispenser via the controller based on a test procedure, which is capable of testing a single particle condition of the droplet dispenser via a testing unite to determine the single particle condition is fulfilled when an ejection region of the nozzle includes one single particle of the particles and eth sedimentation region adjacent to and upstream the ejection region is free the particles, wherein in the sedimentation region the particles are displaced to the ejection region by sedimentation between the step of detecting the presence of the particles and a step of controlling the droplet dispenser; and 
 operating the droplet dispenser via the controller, wherein, in dependency on the single particle condition fulfilment, one of the droplets is dispensed from the droplet dispenser onto the target or at least one of the droplets is discarded from the droplet dispenser into a collection reservoir, wherein 
 when the step of testing the single particle condition with the ejection region is not fulfilled, testing the single particle condition further includes 
 reducing the ejection region according to an ejection region subsection and determining whether a current ejection region subsection includes one single particle and the sedimentation region adjacent to the current ejection region subsection is free of particles, and 
 dispensing a fractional droplet having a fraction of the first droplet volume onto the target if the single particle condition is fulfilled with the current ejection region subsection. 
 
     
     
       16. The method according to  claim 15 , wherein, if the step of testing the single particle condition with the ejection region subsection is not fulfilled, testing the single particle condition further includes
 further reducing the ejection region and testing the single particle condition with the further reduced ejection region subsection. 
 
     
     
       17. The method according to  claim 15 , wherein
 the fraction of the first droplet volume is obtained by determining the position of the single particle in the ejection region subsection and estimating the fractional droplet volume based on the particle position in a mapping step. 
 
     
     
       18. A dispenser apparatus, being adapted for dispensing droplets including single particles onto a target, comprising:
 at least one droplet dispenser having a suspension reservoir and a nozzle configured to include a particle suspension, an ejection region and a sedimentation region upstream of the ejection region; 
 a dispenser head arranged for carrying the at least one droplet dispenser; 
 a nozzle camera arranged for detecting particles in the nozzle; 
 a control device arranged electrical communication with the nozzle camera and for controlling the at least one droplet dispenser; and 
 a testing unit coupled with the nozzle camera and with the control device and being adapted for (i) testing a single particle condition of the droplet dispenser, wherein during testing it is determined whether the ejection region of the nozzle includes one single particle and the sedimentation region adjacent to the ejection region is free of particles, wherein in the sedimentation region the particles are displaced to the ejection region by sedimentation during an operation delay interval between a step of detecting the presence of particles and a step of operating the droplet dispenser, and (ii) testing at least one of a zero particle condition of the droplet dispenser, wherein it is determined whether a predetermined volume equal to or larger than a 2-fold volume of the ejection region beginning at a tip of the nozzle of the droplet dispenser to the sedimentation region is free of particles to be dispensed, and a particle type condition, wherein it is determined whether detected particles have a predetermined particle type identified by at least one of size, shape, colour emission and absorption, wherein 
 the control device is adapted for controlling the droplet dispenser based on the single particle condition, at least one of the zero particle condition and the particle type condition, a droplet is dispensed onto the target or discarded into a collection reservoir. 
 
     
     
       19. The dispenser apparatus according to  claim 18 , wherein
 the testing unit includes an image data storage being adapted for storing image data of the ejection region and the sedimentation region.